network ip assignment

Understanding IP Address Assignment: A Complete Guide

Introduction

In today's interconnected world, where almost every aspect of our lives relies on the internet, understanding IP address assignment is crucial for ensuring online security and efficient network management. An IP address serves as a unique identifier for devices connected to a network, allowing them to communicate with each other and access the vast resources available on the internet. Whether you're a technical professional, a network administrator, or simply an internet user, having a solid grasp of how IP addresses are assigned within the same network can greatly enhance your ability to troubleshoot connectivity issues and protect your data.

The Basics of IP Addresses

Before delving into the intricacies of IP address assignment in the same network, it's important to have a basic understanding of what an IP address is. In simple terms, an IP address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It consists of four sets of numbers separated by periods (e.g., 192.168.0.1) and can be either IPv4 or IPv6 format.

IP Address Allocation Methods

There are several methods used for allocating IP addresses within a network. One commonly used method is Dynamic Host Configuration Protocol (DHCP). DHCP allows devices to obtain an IP address automatically from a central server, simplifying the process of managing large networks. Another method is static IP address assignment, where an administrator manually assigns specific addresses to devices within the network. This method provides more control but requires careful planning and documentation.

Considerations for Efficient IP Address Allocation

Efficient allocation of IP addresses is essential for optimizing network performance and avoiding conflicts. When assigning IP addresses, administrators need to consider factors such as subnetting, addressing schemes, and future scalability requirements. By carefully planning the allocation process and implementing best practices such as using private IP ranges and avoiding overlapping subnets, administrators can ensure smooth operation of their networks without running out of available addresses.

IP Address Assignment in the Same Network

When two routers are connected within the same network, they need to obtain unique IP addresses to communicate effectively. This can be achieved through various methods, such as using different subnets or configuring one router as a DHCP server and the other as a client. Understanding how IP address assignment works in this scenario is crucial for maintaining proper network functionality and avoiding conflicts.

Basics of IP Addresses

IP addresses are a fundamental aspect of computer networking that allows devices to communicate with each other over the internet. An IP address, short for Internet Protocol address, is a unique numerical label assigned to each device connected to a network. It serves as an identifier for both the source and destination of data packets transmitted across the network.

The structure of an IP address consists of four sets of numbers separated by periods (e.g., 192.168.0.1). Each set can range from 0 to 255, resulting in a total of approximately 4.3 billion possible unique combinations for IPv4 addresses. However, with the increasing number of devices connected to the internet, IPv6 addresses were introduced to provide a significantly larger pool of available addresses.

IPv4 addresses are still predominantly used today and are divided into different classes based on their range and purpose. Class A addresses have the first octet reserved for network identification, allowing for a large number of hosts within each network. Class B addresses reserve the first two octets for network identification and provide a balance between network size and number of hosts per network. Class C addresses allocate the first three octets for network identification and are commonly used in small networks.

With the depletion of available IPv4 addresses, IPv6 was developed to overcome this limitation by utilizing 128-bit addressing scheme, providing an enormous pool of potential IP addresses - approximately 3.4 x 10^38 unique combinations.

IPv6 addresses are represented in hexadecimal format separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). The longer length allows for more efficient routing and eliminates the need for Network Address Translation (NAT) due to its vast address space.

Understanding these basics is essential when it comes to assigning IP addresses in a network. Network administrators must consider various factors such as the number of devices, network topology, and security requirements when deciding on the IP address allocation method.

In the next section, we will explore different methods of IP address assignment, including Dynamic Host Configuration Protocol (DHCP) and static IP address assignment. These methods play a crucial role in efficiently managing IP addresses within a network and ensuring seamless communication between devices.

Methods of IP Address Assignment

IP address assignment is a crucial aspect of network management and plays a vital role in ensuring seamless connectivity and efficient data transfer. There are primarily two methods of assigning IP addresses in a network: dynamic IP address assignment using the Dynamic Host Configuration Protocol (DHCP) and static IP address assignment.

Dynamic IP Address Assignment using DHCP

Dynamic IP address assignment is the most commonly used method in modern networks. It involves the use of DHCP servers, which dynamically allocate IP addresses to devices on the network. When a device connects to the network, it sends a DHCP request to the DHCP server, which responds by assigning an available IP address from its pool.

One of the key benefits of dynamic IP address assignment is its simplicity and scalability. With dynamic allocation, network administrators don't have to manually configure each device's IP address. Instead, they can rely on the DHCP server to handle this task automatically. This significantly reduces administrative overhead and makes it easier to manage large networks with numerous devices.

Another advantage of dynamic allocation is that it allows for efficient utilization of available IP addresses. Since addresses are assigned on-demand, there is no wastage of unused addresses. This is particularly beneficial in scenarios where devices frequently connect and disconnect from the network, such as in public Wi-Fi hotspots or corporate environments with a high turnover rate.

However, dynamic allocation does have some drawbacks as well. One potential issue is that devices may receive different IP addresses each time they connect to the network. While this might not be an issue for most users, it can cause problems for certain applications or services that rely on consistent addressing.

Additionally, dynamic allocation introduces a dependency on the DHCP server. If the server goes down or becomes unreachable, devices will not be able to obtain an IP address and will be unable to connect to the network. To mitigate this risk, redundant DHCP servers can be deployed for high availability.

Static IP Address Assignment

Static IP address assignment involves manually configuring each device's IP address within the network. Unlike dynamic allocation, where addresses are assigned on-demand, static assignment requires administrators to assign a specific IP address to each device.

One of the main advantages of static IP address assignment is stability. Since devices have fixed addresses, there is no risk of them receiving different addresses each time they connect to the network. This can be beneficial for applications or services that require consistent addressing, such as servers hosting websites or databases.

Static assignment also provides greater control over network resources. Administrators can allocate specific IP addresses to devices based on their requirements or security considerations. For example, critical servers or network infrastructure devices can be assigned static addresses to ensure their availability and ease of management.

However, static IP address assignment has its limitations as well. It can be time-consuming and error-prone, especially in large networks with numerous devices. Any changes to the network topology or addition/removal of devices may require manual reconfiguration of IP addresses, which can be a tedious task.

Furthermore, static allocation can lead to inefficient utilization of available IP addresses. Each device is assigned a fixed address regardless of whether it is actively using the network or not. This can result in wastage of unused addresses and may pose challenges in scenarios where addressing space is limited.

In order to efficiently allocate IP addresses within a network, there are several important considerations that need to be taken into account. By carefully planning and managing the allocation process, network administrators can optimize their IP address usage and ensure smooth operation of their network.

One of the key factors to consider when assigning IP addresses is the size of the network. The number of devices that will be connected to the network determines the range of IP addresses that will be required. It is essential to accurately estimate the number of devices that will need an IP address in order to avoid running out of available addresses or wasting them unnecessarily.

Another consideration is the type of devices that will be connected to the network. Different devices have different requirements in terms of IP address assignment. For example, servers and other critical infrastructure typically require static IP addresses for stability and ease of access. On the other hand, client devices such as laptops and smartphones can often use dynamic IP addresses assigned by a DHCP server.

The physical layout of the network is also an important factor to consider. In larger networks with multiple subnets or VLANs, it may be necessary to segment IP address ranges accordingly. This allows for better organization and management of IP addresses, making it easier to troubleshoot issues and implement security measures.

Security is another crucial consideration when allocating IP addresses. Network administrators should implement measures such as firewalls and intrusion detection systems to protect against unauthorized access or malicious activities. Additionally, assigning unique IP addresses to each device enables better tracking and monitoring, facilitating quick identification and response in case of any security incidents.

Efficient utilization of IP address ranges can also be achieved through proper documentation and record-keeping. Maintaining an up-to-date inventory of all assigned IP addresses helps prevent conflicts or duplicate assignments. It also aids in identifying unused or underutilized portions of the address space, allowing for more efficient allocation in the future.

Furthermore, considering future growth and scalability is essential when allocating IP addresses. Network administrators should plan for potential expansion and allocate IP address ranges accordingly. This foresight ensures that there will be sufficient addresses available to accommodate new devices or additional network segments without disrupting the existing infrastructure.

In any network, the assignment of IP addresses is a crucial aspect that allows devices to communicate with each other effectively. When it comes to IP address assignment in the same network, there are specific considerations and methods to ensure efficient allocation. In this section, we will delve into how two routers in the same network obtain IP addresses and discuss subnetting and IP address range distribution.

To understand how two routers in the same network obtain IP addresses, it's essential to grasp the concept of subnetting. Subnetting involves dividing a larger network into smaller subnetworks or subnets. Each subnet has its own unique range of IP addresses that can be assigned to devices within that particular subnet. This division helps manage and organize large networks efficiently.

When it comes to assigning IP addresses within a subnet, there are various methods available. One common method is manual or static IP address assignment. In this approach, network administrators manually assign a specific IP address to each device within the network. Static IP addresses are typically used for devices that require consistent connectivity and need to be easily identifiable on the network.

Another widely used method for IP address assignment is Dynamic Host Configuration Protocol (DHCP). DHCP is a networking protocol that enables automatic allocation of IP addresses within a network. With DHCP, a server is responsible for assigning IP addresses dynamically as devices connect to the network. This dynamic allocation ensures efficient utilization of available IP addresses by temporarily assigning them to connected devices when needed.

When considering efficient allocation of IP addresses in the same network, several factors come into play. One important consideration is proper planning and design of subnets based on anticipated device count and future growth projections. By carefully analyzing these factors, administrators can allocate appropriate ranges of IP addresses for each subnet, minimizing wastage and ensuring scalability.

Additionally, implementing proper security measures is crucial when assigning IP addresses in the same network. Network administrators should consider implementing firewalls, access control lists (ACLs), and other security mechanisms to protect against unauthorized access and potential IP address conflicts.

Furthermore, monitoring and managing IP address usage is essential for efficient allocation. Regular audits can help identify any unused or underutilized IP addresses that can be reclaimed and allocated to devices as needed. This proactive approach ensures that IP addresses are utilized optimally within the network.

The proper assignment of IP addresses is crucial for maintaining network security and efficiency. Throughout this guide, we have covered the basics of IP addresses, explored different methods of IP address assignment, and discussed considerations for efficient allocation.

In conclusion, understanding IP address assignment in the same network is essential for network administrators and technical professionals. By following proper allocation methods such as DHCP or static IP assignment, organizations can ensure that each device on their network has a unique identifier. This not only enables effective communication and data transfer but also enhances network security by preventing unauthorized access.

Moreover, considering factors like subnetting, scalability, and future growth can help optimize IP address allocation within a network. Network administrators should carefully plan and allocate IP addresses to avoid conflicts or wastage of resources.

Overall, a well-managed IP address assignment process is vital for the smooth functioning of any network. It allows devices to connect seamlessly while ensuring security measures are in place. By adhering to best practices and staying updated with advancements in networking technology, organizations can effectively manage their IP address assignments.

In conclusion, this guide has provided a comprehensive overview of IP address assignment in the same network. We hope it has equipped you with the knowledge needed to make informed decisions regarding your network's IP address allocation. Remember that proper IP address assignment is not only important for connectivity but also plays a significant role in maintaining online security and optimizing network performance.

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Steve's Smart Home Networking Guide

Practical Home Networking and Home Automation

IP Addresses on Home Networks – A Beginner’s Guide

All devices connected to a home network require an IP (Internet Protocol )address.

Understanding IP addresses is essential for configuring devices to work on your network, troubleshooting network issues etc.

What are IP Addresses?

Devices requiring an IP addresses is no different from telephones requiring a telephone number , or a house requiring an address.

An IP address is essential to identify a device on the network so that it can receive data e.g movies, emails etc in just the same way a a telephone number is required to receive phone calls.

Just as house numbers have a particular format e.g. 25,King street, etc and phone numbers have a structure like area code + local number then so to do IP addresses.

IP Address Types

There are two type of IP address- IPv4 which is the original and older address type and IPv6 which is the newer type.

Currently home networks use the IPv4 address type although you will also see IPV6 addresses assigned, but not really used.

Because IPv4 addresses are what home networks currently use we will concentrate on these addresses in this tutorial.

IPV4 Addresses

An IP address ( IPv4 ) consist of 4 numbers separated by a dot and look like this:

192.168.1.1

All IP addresses on a home network need to be unique which is important to note if you need to manually allocate them.

The right most number is the important number as far as most people are concerned, and will be different for each device on the home network

The screen shot below shows a device map with the IP address allocation for part of my home network. Notice which part of the address changes.

 Home Network IP address Assignment

IP address can be assigned:

• Automatically

Manual IP Address Assignment

Manually assigned addresses are known as static addresses.

When assigning a static IP address you will also need to enter other important address information.

The screen shot below shows the static address assignment on my Windows 10 computer however all devices have a similar form for the IP address assignment.

1. My home network use the network address 192.168.1 (first three numbers) also common is 192.168.0 and 10.x.x.x

2. The default gateway is the address of your home router. This is assigned to the router as a static IP address. Common gateway addresses use the first or last addresses of the range which are 1 and 254 .

3. The subnet mask is important as is usually 255.255.255.0

4. You need the address of 1 DNS server to access websites on the Internet. The Google DNS server is available to use for free but you can use your ISP DNS servers.

5. You can choose to manually assign the DNS addresses and automatically assign the IP address or vice versa.

6. Make a note of the addresses you assign so as to avoid address conflicts .

Automatic IP Address Assignment- DHCP

This is the default configuration on most devices.

This is what it looks like on my Windows 10 computer.

On home networks this service is provided by the home router which has DHCP enabled by default.

If no DHCP server is available Windows machines (some versions) will auto assign an address. This address starts with 169.254

e.g. 169.254.0.1

No DNS server address will be allocated which means that you will not have access to the internet unless you know the IP address of the server.

Finding Your IP Address,Gateway Address etc?

You may need to find out what DNS servers you are using or the IP or MAC address of:

• Your Home Router.
• Your own computer/tablet/phone

The main tool you use is the ipconfig (windows) or ifconfig (linux) tool.

The screen shot below shows the ipconfig command use with the /all switch. i.e. ipconfig/all

Common Questions and Basic Troubleshooting

Q- what happens if dhcp fails.

A- Because IP addresses are leased from the DHCP server your client machine will keep its existing address until the lease expires usually 1 day. and so will run normally for a while.

New machines joining the network will not get an IP address and may auto assign one depending on the device.

They will not work with existing machines and because they don’t have a DNS server address they wont be able to access the Internet.

Q -How do I know if I have a static IP address or a automatically assigned one?

A- You can look at the network adapter properties or on Windows open a command line and type

ipconfig /all

If you see the entry DHCP Enabled .. No then you are using a static IP address.

Q- What happens if a have two DHCP servers on my Home Network?

A- This may cause strange behaviour and is to be avoided. On home networks the home router provides the DHCP service by default. If you try to reuse old routers as Wireless access points then you can run into this problem

Q -What is The IP address of my router or default gateway?

A- You can find it using the ipconfig command line tool (ifconfig on Linux) as shown above. When viewing your configuration some devices refer to it as the default router whereas other use the term default gateway.

In the screen shot above it is 192.168.1.254

Your home router generally comes with a static IP address assigned. Common addresses are:

192.168.1.254 and 192.168.1.1

However you can change it if you want, but because this is the main device on the home network I would leave it as it is.  If you do change it you will need to make changes on any devices that use a static IP address.

Q- What happens if I assign the same IP address to two separate devices?

A- You get an IP address conflict and the devices wont work.

Q- Do I need to subnet my Home Network?

A- Almost certainly no. See Home network Subnet masks explained .

Q- What is ARP?

A- ARP stands for address resolution protocol and translates an IP address to a MAC address.

Related tutorials and Resources

• How to Setup and Configure your Home Router 
• Setting Up Static IP Addresses on Windows 10
• Understanding DHPC on Home Networks
• Name Resolution on Home Networks
• Setting Up A DNS Server using DNSMasq
• Understanding Multicast DNS
• Home networking Course

I thoroughly enjoyed reading this and other articles on “home networks”. As a long time computer user & developer, I found your writing style refreshing. I look forward to future essays on related topics such as home router configuration, home LAN “tuning” &”trouble shooting”. ~~~ 0:¬ Dan

Very helpful. Thank you. Would you say it is beneficial to assign IP addresses or just allow the system to get on with it?

You should always let the system do it unless you really have a need to do it manually you might find this useful https://youtu.be/2yOMNugsdE0 rgds Steve

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Network Design – Designing Advanced IP Addressing

October 19, 2021 By Paul Browning Leave a Comment

This blog post covers the following network design topics:

• Summarizable and structured addressing designs
• IPv6 for Enterprise Campus design considerations

When designing IP addressing at a professional level, several issues must be taken into consideration. This blog post will cover generic IP addressing designs, including subnets and summarizable blocks design recommendations, address planning, and advanced addressing concepts, in addition to IPv6 design considerations, which will be covered in the last section of the post.

Importance of IP Addressing for Network Design

One of the major concerns in the network design phase is ensuring that the IP addressing scheme is properly designed. This aspect should be carefully planned and an implementation strategy should exist for the structural, hierarchical, and contiguous allocation of IP address blocks. A solid addressing scheme should be hierarchical, structural, and modular .

These features will add value to the continually improving concept of the Enterprise Campus design. This is also important in scaling any of the dynamic routing protocols. A solid IP addressing scheme helps routing protocols function in an optimal manner, using RIPv2, EIGRP, OSPF, or BGP. Facilitating summarization and the ability to summarize addresses provides several advantages for the network:

• Shorter Access Control Lists (ACLs)
• Reduces the overhead on routers (the performance difference is noticeable, especially on older routers)
• Faster convergence of routing protocols
• Addresses can be summarized to help isolate trouble domains
• Overall improvement of network stability

Address summarization is also important when there is a need to distribute addresses from one routing domain into another, as it impacts both the configuration effort and the overhead in the routing processing. In addition, having a solid IP addressing scheme not only makes ACLs easier to implement and more efficient for security, policy, and QoS purposes, but also it facilitates advanced routing policies and techniques (such as zone-based policy firewalls), where modular components and object groupings that are based on the defined IP addressing schemes can be created.

Solid IP address planning supports several features in an organization:

• Route summarization
• A more scalable network
• A more stable network
• Faster convergence

Subnet Network Design Recommendations

The importance of IP addressing is reflected in the new requirements that demand greater consideration of IP addressing, as the following examples illustrate:

• The transition to VoIP Telephony and the additional subnet ranges required to support voice services. Data and voice VLANs are usually segregated, and in some scenarios, twice as many subnets may be needed when implementing Telephony in the network .
• Layer 3 switching at the edge, replacing the Layer 2 switching with multi-layer switches. This involves more subnets needed at the Enterprise Edge, so t he number of smaller subnets will increase . There should be as little re-addressing as necessary, and making efficient use of the address space should be a priority. Sometimes, Layer 3 switching moved to the edge will involve a redesign of the IP addressing hierarchy.
• The company’s needs are changing and sometimes servers will be isolated by functions or roles (also called segmentation). For example, the accounting server, the development subnets, and the call-center subnets can be separated from an addressing standpoint. Identifying the subnets and ACLs based on corporate requirements can also add complexity to the environment .
• Many organizations use technologies like Network Admission Control (NAC), Cisco 802.1x (IBNS), or Microsoft NAP. These types of deployments will be dynamically assigning VLANs based on the user login or port-based authentication. In this situation, an ACL can actually manage connectivity to different servers and network resources based on the source subnet (which is based on the user role). Using NAC over a wired or wireless network will add more complexity to the IP addressing scheme.
• Many network topologies involve having separated VLANs (i.e., data, voice, and wireless). Using 802.1x may also involve a guest VLAN or a restricted VLAN , and authorization policies can be assigned based on VLAN membership from an Authentication, Authorization, and Accounting (AAA) server.
• Using role-based security techniques might require different sets of VPN clients, such as administrators, customers, vendors, guests, or extranets, so different groups can be implemented for different VPN client pools. This role-based access can be managed through a group password technique for each Cisco VPN client; every group can be assigned a VPN endpoint address from a different pool of addresses. If the pools are subnets of a summarizable block, then routing traffic back to the client can also be accomplished in a simplified fashion.
• Network designers should also consider that Network Address Translation (NAT) and Port Address Translation (PAT) can be applied on customer edge routers (often on the PIX firewall or on the ASA devices). NAT and PAT should not be used internally on the LAN or within the Enterprise Network to simplify the troubleshooting process. NAT can be used in a data center to support the Out-of-Band (OOB) management of the VLAN (i.e., on devices that cannot route or cannot find a default gateway for the OOB management of the VLAN).

You can read Ciscos network design guide here .

Summarization

After planning the network design for a IPv4 addressing scheme and determining the number and types of necessary addresses, a hierarchical design might be necessary. This design is useful when finding a scalable solution for a large organization and this involves address summarization. Summarization reduces the number of routes in the routing table and involves taking a series of network prefixes and representing them as a single summary address. It also involves reducing the CPU load and the memory utilization on network devices. In addition, this technique reduces processing overhead because routers advertise a single prefix instead of many smaller ones.

A summarizable address is one that contains blocks with sequential numbers in one of the octets . The sequential patterns must fit a binary bit pattern, with X numbers in a row, where X is a power of 2. The first number in this sequence must be a multiple of X. For example, 128 numbers in a row could be summarized with multiples starting at 0 or 128. If there are 64 numbers in a row (2 6 ), these will be represented in multiples of 64, such as 0, 64, 128, or 192, and 32 numbers in a row can be summarized with the multiples 0, 32, 64, and so on. This process can be easily accomplished using software subnet calculators.

Another planning aspect of summarizable blocks involves medium or large blocks of server farms or data centers. Servers can be grouped based on their functions and on their level of mission criticality, and they can all be in different subnets. In addition, with servers that are attached to different Access Layer switches, it is easier to assign subnets that will provide a perfect pattern for wildcarding in the ACLs. Simple wildcard rules and efficient ACLs are desired, as complex ACLs are very difficult to deal with, especially for new engineers who must take over an existing project.

When implementing the hierarchical addressing scheme for network design, it is important to have a good understanding of the math behind it and how route summarization works. Below is an example of combining a group of Class C addresses into an aggregate address. Summarization is a way to represent several networks in a single summarized route. In a real-world scenario, a subnet calculator can be used to automatically generate the most appropriate aggregate route from a group of addresses.

In this example, the Enterprise Campus backbone (Core Layer) submodule is connected to several other buildings. In a single building, there are several networks in use:

• A network for the server farm
• A network for the management area
• A few networks for the Access Layer submodule (that serve several departments)

The goal is to take all of these networks and aggregate them into one single address that can be stored at the edge distribution submodule or at the Core Layer of the network. The first thing to understand when implementing a hierarchical addressing structure is the use of continuous blocks of IP addresses . In this example, the addresses 192.100.168.0 through 192.100.175.0 are used:

In this scenario, network design summarization will be based on a location where all of the uppermost bits are identical. Looking at the first address above, the first 8 bits equal the decimal 192, the next 8 bits equal the decimal 100, and the last 8 bits are represented by 0. The only octet that changes is the third one; to be more specific, only the last 3 bits in that octet change when going through the address range.

The summarization process requires writing the third octet in binary format and then looking for the common bits on the left side. In the example above, all of the bits are identical up to the last three bits in the third octet. With 21 identical bits, all of the addresses will be summarized to 192.100.168.0/21.

After deciding on a hierarchical addressing design and understanding the math involved in this process, the next approach will be a modular and scalable design, which will involve deciding how to divide the organization (i.e., Enterprise Network modules, submodules, and remote locations) in terms of addressing. This includes deciding whether to apply a hierarchical address to each module/submodule or to the entire Enterprise Network.

Another aspect to consider is the way summarization may affect the routing protocols used. Summarization usually affects routing because it reduces the size of the routing tables, the processor, and memory utilization, and it offers a much faster convergence of the routed network. The following are the most important advantages of using route aggregation:

• Lower device processing overhead
• Improved network stability
• Ease of future growth

Figure 1 below offers another example of a large organization network design using a campus with multiple buildings:

Figure 1 – Network Design Addressing for a Large Organization with Multiple Buildings

The internal private addressing will use the popular 10.0.0.0/8 range. Within the organization’s domain, two separate building infrastructures (on the same campus or in remote buildings) will be aggregated using the 10.128.0.0/16 and 10.129.0.0/16 ranges.

Going deeper within each building, the addressing scheme can be broken down within different departments, using the 10.128.1.0, 10.128.2.0 or the 10.129.1.0, 10.128.2.0 networks with a 24-bit mask. Because of the scalable design, another tier could be included above the departmental addresses that would be within the 10.129.0.0/21 range, for example. Moving beyond that point leads to the Enterprise Edge module and its various submodules (e.g., e-commerce, Internet connectivity, etc.) that can have point-to-point connections to different ISPs. Variable Length Subnet Masking (VLSM) can be used to break down the addressing scheme further.

To summarize, from a network designer standpoint, it is very important to tie the addressing scheme to the modular Enterprise Network design . The advantages of using route summarization and aggregation are numerous but the most important ones are as follows:

• Isolates changes to the topology to a particular module
• Isolates routing updates to a particular module
• Fewer updates need to be sent up the hierarchy (preventing all of the updates from going through the entire network infrastructure)
• Lower overall recalculation of the entire network when links fail (e.g., a change in a routing table does not converge to the entire network); for example, route flapping in a particular department is constrained within the specific department and does not have a cascading effect on other modules (considering the example above)
• Narrow scope of route advertisement propagation
• Summarized module is easier to troubleshoot

Routing Protocols and Summarization for Network Design

Different routing protocols handle summarization in different manners. Routing Information Protocol (RIP) version 2 (RIPv2) has classful origins (it summarizes by default), although it can act in a classless manner because it sends subnet mask information in the routing updates.

Because of its classful origins, RIPv2 performs automatic summarization on classful boundaries, so any time RIPv2 is advertising a network across a different major network boundary, it summarizes to the classful mask without asking for permission. This can lead to big problems in the routing infrastructure of discontiguous networks. RIPv2’s automatic summarization behavior should be disabled in many situations to gain full control of the network routing operations.

In addition to the automatic summarization feature, RIPv2 allows for manual route summarization to be performed at the interface level . The recommendation is to disable automatic summarization and configure manual summarization where necessary. RIPv2 does not allow for summarization below the classful address. The next example involves the following prefixes:

210.22.10.0/24

210.22.9.0/24

210.22.8.0/24

RIPv2 will not allow the summarization of addresses above a /22 address because these are Class C addresses, and this would involve trying to summarize beneath this class. This is a limitation due to the classful origin of RIP.

EIGRP functions similar to RIPv2 regarding summarization, as EIGRP also has classful origins because it is an enhanced version of the Interior Gateway Routing Protocol (IGRP). EIGRP automatically summarizes on classful boundaries and, just like with RIPv2, this feature can be disabled and manual summarization can be configured on specific interfaces. The biggest issue with this behavior is that there might be discontiguous networks and this could cause problems with any of the automatic summarization mechanisms described.

Figure 2 – Discontiguous Network Issue

An example of a discontiguous network issue is illustrated in Figure 2 above. The 172.16.10.0/24 subnet is on the left side and the 172.16.12.0/24 subnet is on the right side. These networks are divided by a different major network in the middle (172.20.60.0/24), which causes a problem. Applying EIGRP in this scenario, automatic summarization will be enabled by default, with summarization toward the middle of the topology (172.16.0.0) from both sides, and this will cause great confusion to that device. As a result of this confusion, the device might send one packet to the left side and one packet to the right side, so there will be packets going in the wrong direction to get to a particular destination. To solve this issue, the automatic summarization feature should be disabled in discontiguous networks. Another possible fix to this problem is designing the addressing infrastructure better so that no discontiguous subnets are present.

OSPF does not have an automatic summarization feature but two different forms of summarization can be designed:

• Summarization between the internal areas
• Summarization from another separate domain

Two separate commands are used to handle these different summarization types. Summarizing from one area to another involves a Type 3 Link-State Advertisement (LSA). Summarizing from another domain involves two types of LSAs in the summarization process: a Type 4 LSA, which advertises the existence of the summarizing device (e.g. the OSPF Autonomous System Border Router – ASBR), and the actual summary of information, carried in a Type 5 LSA.

Border Gateway Protocol (BGP) uses a single type of summarization called aggregation , and this is accomplished during the routing process. BGP is used to summarize automatically, just like RIPv2 and EIGRP, but this behavior has been automatically disabled by the 12.2(8)T IOS code.

Variable Length Subnet Masking and Structured Addressing

A structured addressing plan involves the concept of Variable Length Subnet Masking (VLSM), a technology that all of the modern routing protocols can easily handle. VLSM provides efficiency, as it disseminates an addressing plan that does not waste address space (i.e., it assigns only the number of addresses needed for a certain subnetwork). VLSM also accommodates efficient summarization. The most important benefits of VLSM and summarization include the following:

• Less CPU utilization on network devices
• Less memory utilization on network devices
• Smaller convergence domains

Figure 3 – VLSM Example (Part 1)

VLSM functions by taking unused subnets from the address space used and further subnets them. Figure 3 above starts with the major network of 172.16.0.0/16 (not shown in the example), which is initially subnetted using a 24-bit mask, resulting in two large subnets on the two router interfaces (Fa0/0 and Fa0/1), 172.16.1.0/24 and 172.16.2.0/24, respectively. Two key formulas can be used when calculating the number of subnets and hosts using VLSM. An example of the subnet and host split in the address is shown below in Figure 4:

Figure 4 – VLSM Subnet and Host Split

The formula for calculating the number of subnets is 2 s , where “s” is the number of borrowed subnet bits. In Figure 3.3 above, the network expanded from a /16 network to a /24 network by borrowing 8 bits. This means 2 8 = 256 subnets can be created with this scheme.

The formula for calculating the number of hosts that can exist in a particular subnet is 2 h -2, where “h” is the number of host bits. Two hosts are subtracted from the 2 h formula because the all-zeros host portion of the address represents the major network itself and the all-ones host portion of the address represents the broadcast address for the specific segment, as illustrated below:

• Major networks (all zeros in the host portion): 172.16.1.0 and 172.16.2.0
• Broadcast networks (all ones in the host portion): 172.16.1.255 and 172.16.2.255

After summarizing the 172.16.0.0/16 address space into 172.16.1.0/24 and 172.16.2.0/24, further subnetting might be needed to accommodate smaller networks, which can be achieved by taking one of the next available subnets (after the subnetting process), for example, 172.16.3.0/24. This will create additional subnets such as those below:

172.16.3.32/27

172.16.3.64/27

The /27 subnets are suitable for smaller networks and can accommodate the number of machines in those areas. The number of hosts that can be accommodated is 2 5 -2=30.

Figure 5 – VLSM Example (Part 2)

A subnet might be needed for the point-to-point link that will connect two network areas, and this can be accomplished by further subnetting one of the available subnets in the /27 scheme, for example 172.16.3.96/27. This can be subnetted with a /30 to obtain 172.16.3.100/30, which offers just two host addresses: 172.16.3.101 and 172.16.3.102. This scheme perfectly suits the needs for the point-to-point connections (one address for each end of the link). By performing VLSM calculations, subnets that can accommodate just the right number of hosts in a particular area can be obtained.

Private versus Public Addressing

As a network design expert, after determining the number of necessary IP addresses, the next big decision is to find out whether private, public, or a combination of private and public addresses will be used. Private internetwork addresses are defined in RFC 1918 and are used internally within the network. From a real-world standpoint, because of the limitation of the number of public IP addresses, NAT techniques are usually used to translate the private internal numbers to external public addresses. Internally, one of the following three ranges of addresses can be used:

• 0.0.0/8 (10.0.0.0 to 10.255.255.255), usually used in large organizations
• 16.0.0/12 (172.16.0.0 to 172.31.255.255), usually used in medium organizations
• 168.0.0/16 (192.168.0.0 to 192.168.255.255), usually used in small organizations

Any address that falls within the three private address ranges cannot be routed on the Internet. Service Provider Edge devices usually have policies and ACLs configured to ensure that any packet containing a private address that arrives at an inbound interface will be dropped.

All of the other addresses are public addresses that are allocated to ISPs or other point of presence nodes on the Internet. ISPs can then assign Class A, B, or C addresses to customers to use on devices that are exposed to the Internet, such as:

• Web servers
• DNS servers
• FTP servers
• Other servers that run public-accessible services

When deciding to use private, public, or a combination of private and public addresses for your network design, one of the following four types of connections will be used:

• No Internet connectivity
• Only one public address (or a few) for users to access the Web
• Web access for users and public-accessible servers
• Every end-system has a public IP address

No Internet connectivity would imply that all of the connections between the locations are private links and the organization would not be connected to the Internet in any of its nodes. In this case, there is no need for any public IP addresses because the entire address scheme can be from the private address ranges.

Another situation would be the one in which there is Internet connectivity from all of the organization’s locations but there are no servers to run public-accessible services (e.g., Web, FTP, or others). In this case, a public IP address is needed that will allow users to access the Web. NAT can be used to translate traffic from the internal network to the outside network, so the internal networks contain only private IP addresses and the external link can use just one public address.

The third scenario is one of the most common, especially when considering the growth of enterprise networking. This involves having user Internet connectivity (just like in the previous scenario) but also having public-accessible servers. Public IP addresses must be used to connect to the Internet and access specific servers (e.g., Web, FTP, DNS, and others). The internal network should use private IP addresses and NAT to translate them into public addresses.

The most highly unlikely scenario would be the one in which every end-system is publicly accessible from the global Internet . This is a dangerous situation because the entire network is exposed to Internet access and this implies high security risks. To mitigate these risks, strong firewall protection policies must be implemented in every location. In addition to the security issues, this scenario is also not very effective because many IP addresses are wasted and this is very expensive. All of these factors make this scenario one not to be used in modern networks.

The two most common solutions from the scenarios presented above are as follows:

• One or a few public addresses for users to access the Web
• A few public addresses that provide Web access for users and public-accessible servers

Both scenarios imply using private internal addresses and NAT to reach outside networks.

For a deeper analysis of these aspects, it is useful to focus on how they map to the Cisco Enterprise Architecture model and where private and public addresses should be used, which is illustrated in Figure 6 below:

Figure 6 – Cisco Enterprise Architecture Model Addressing Scheme

First, in the figure above, assume that there is some kind of Internet presence in the organization that offers services either to internal users in the Access Layer submodule or to different public-accessible servers (e.g., Web, FTP, or others) in the Enterprise Edge module. Regardless of what modules receive Internet access, NAT is run in the edge distribution submodule to translate between the internal addressing structure used in the Enterprise Campus and the external public IP addressing structure. NAT mechanisms can also be used in the Enterprise Edge module.

Using the 10.0.0.0/8 range internally, both in the Enterprise Campus module and in the network management submodule, Enterprise Campus devices that use private IP addresses include all of its component submodules:

• Access Layer
• Distribution Layer
• Server farm

The edge distribution submodule will use a combination of private and public IP addresses. The Enterprise Edge module will use a combination of private and public addresses, depending on each submodule. The remote access submodule can use a combination of private and public addresses but it will need to support some kind of NAT techniques. The WAN submodule can use either private addresses (when connecting to other remote sites) or public addresses (when connected to outside locations for a backup solution).

Address Planning

An important issue in the IP addressing design is how the addresses will be assigned. One way would be to use static assigning and the other way would be to use dynamic protocols such as the Dynamic Host Configuration Protocol (DHCP). Deciding on the address allocation method requires answering the following questions:

• How many end-systems are there?

For a small number of hosts (less than 50), consider using statically/manually assigned addresses; however, if there are several hundred systems, use DHCP to speed up the address allocation process (i.e., avoid manual address allocation).

• What does the security policy demand?

Some organizations demand the use of static IP addressing for every host or for every node to create a more secure environment. For example, an outsider cannot plug in a station to the network, automatically get an IP address, and have access to internal resources. The organization’s security policy might demand static addressing, regardless of the network size.

• What is the likelihood of renumbering?

This includes the possibility of acquisitions and mergers in the near future. If the likelihood of renumbering is high, DHCP should be used.

• Are there any high availability demands?

If the organization has high availability demands, DHCP should be used in a redundant server architecture.

In addition, static addressing should always be used on certain modules in certain devices:

• Corporate servers
• Network management workstations
• Standalone servers in the Access Layer submodule
• Printers and other peripheral devices in the Access Layer submodule
• Public-accessible servers in the Enterprise Edge module
• Remote Access Layer submodule devices
• WAN submodule devices

Role-Based Addressing

From a Cisco standpoint, the best way to implement role-based addressing is to have it mapped to the corporate structure or to the roles of the servers or end-user stations. Using an example based on the 10.0.0.0/8 network, consider the first octet to be the major network number, the second octet to be the number assigned to the closet (i.e., the server room or wiring closets throughout the organization), the third octet to be the VLAN numbers, and the last octet to be the number of hosts. An address of 10.X.Y.Z would imply the following octet definitions:

• X = closet numbers
• Y = VLAN numbers
• Z = host numbers

This is an easy mechanism that can be used with Layer 3 closets. Role-based addressing avoids binary arithmetic , so if there are more than 256 closets, for example (more than can be identified in the second octet), some bits can be borrowed from the beginning of the third octet because there will not be 256 VLANs for every switch. Thereafter, advanced binary arithmetic or bit splitting can be used to adapt the addressing structure to specific needs. Bit splitting can be used with routing protocols, as well as route summarization, to help number the necessary summarizable blocks.  In this case, addresses will be split into a network part, an area part, a subnet part, and a host part.

Network designers might not always have the luxury of using the summarizable blocks around simple octet boundaries and sometimes this is not even necessary, especially when some bit splitting techniques would better accommodate the organization and the role-based addressing scheme. This usually involves some binary math, such as the example below:

172.16.aaaassss.sshhhhhh

The first octet is 172 and the second octet is 16. The “a” bits in the third octet identify the area and the “s” bits identify the network subnet or VLAN. Six bits are reserved for the hosts in the forth octet. This offers 62 hosts per VLAN or subnet, or 2 16 -2 (two host addresses will be reserved for the network address – all zeros in the last bits and the broadcast address and all ones in the last bits).

This logical scheme will result in the following address ranges, based on the network areas:

• Area 0: 172.16.0.0 to 172.16.15.255
• Area 1: 172.16.16.0 to 172.16.31.255
• Area 2: 172.16.32.0 to 172.16.47.255

Subnet calculations should be made to ensure that the right type of bit splitting is used to represent the subnet and VLANs. Remember that a good summarization technique is to take the last subnet in every area and divide it so that the /30 subnet can be used for any WAN or point-to-point links. This will maximize the address space so for each WAN link there will be only two addresses with a /30 or .252 subnet mask.

Most organizations have their addressing schemes mapped out onto spreadsheets or included in different reports and stored as part of their documentation for the network topology. This should be done very systematically and hierarchically, regardless of the addressing scheme used. Always take into consideration the possible growth of the company through mergers or acquisitions.

Network Address Translation Applications

Although the goal with IPv6 is to avoid the need for NAT, NAT for IPv4 will still be used for a while. NAT is one of the mechanisms used in the transition from IPv4 to IPv6, so it will not disappear any time soon. In addition, it is a very functional tool for working with IPv4 addressing. NAT and PAT (or NAT Overload) are usually carried out on ASA devices, which have powerful tools to accomplish these tasks in many forms:

• Dynamic NAT
• Identity NAT

A recommended best practice is to try to avoid using NAT on internal networks, except for situations in which NAT is required as a stop-gap measure during mergers or migrations. NAT should not be performed between the Access Layer and the Distribution Layer or between the Distribution Layer and the Core Layer. Following this recommendation will prevent address translation between OSPF areas, for example.

Organizations with a merger in progress usually use the same internal network addressing schemes and these can be managed with NAT overlapping techniques (also referred to as bidirectional NAT), which translates between the two organizations when they have an overlapping internal IP addressing space that uses RFC 1918 addressing.

If there are internal servers or servers in the DMZ that are reached using translated addresses, it is a good practice to isolate these servers into their own address space and VLAN, possibly using private VLANs. NAT is often used to support content load balancing servers, which usually must be isolated by implementing address translation.

NAT can also be used in the data center submodule to support a management VLAN that is Out-of-Band from production traffic. It should also be implemented on devices that cannot route or cannot define a gateway for the management VLAN. This results in smaller management VLANs, not a single large management VLAN that covers the entire data center. In addition, large companies or Internet entities can exchange their summary routes, and then they can translate with NAT blocks into the network. This will offer faster convergence but the downside is an increased troubleshooting process because of the use of NAT or PAT.

PAT is harder to troubleshoot because one or a few IP addresses are used to represent hundreds or even thousands of internal hosts, all using TCP and UDP ports to create logical sockets. This increases the complexity of the troubleshooting process because it is difficult to know what IP address is assigned to a particular host. Each host uses a shared IP address and a port number. If the organization is connected to several different partners or vendors, each partner can be represented by a different NAT block, which can be translated in the organization.

Network Design for IPv6 Addressing

CCDP certification requires a solid understanding of the IP version 6 specifications, addressing, and some of the design issues. The IPv6 protocol is based on RFC 2460. From a network designer standpoint, the most important features offered by IPv6 include the following:

• A 128-bit address space
• Supports hierarchical addressing and auto-configuration
• Every host can have a globally unique IPv6 address; no need for NAT
• Hosts can have multiple addresses
• Efficient fixed header size for IPv6 packets
• Enhanced security and privacy headers
• Improved multicasting and QoS
• Dedicated IPv6 routing protocols: RIPng, OSPFv3, Integrated IS-ISv6, BGP4+
• Every major vendor supports IPv6

IPv6 is a mechanism that was created to overcome the limitations of the current IPv4 standard . One of the major shortcomings of IPv4 is that it uses a 32-bit address space. Because of the classful system and the growth of the Internet, the 32-bit address space has proven to be insufficient. The key factors that led to the evolution of IPv6 were large institutions, Enterprise Networks, and ISPs that demanded a larger pool of IP addresses for different applications and services.

Address Representation

IPv4 uses a 32-bit address space, so it offers around 4.2 billion possible addresses, including the multicast, experimental, and private ones. The IPv6 address space is 128 bits, so it offers around 3.4×10 38 possible addressable nodes. The address space is so large that there are about 5×10 28 addresses per person in the world. IPv6 also gives every user multiple global addresses that can be used for a wide variety of devices (e.g., PDAs, cell phones, and IP-enabled devices). IPv6 addresses will last a very long time. An IPv6 packet contains the following fields, as depicted in Figure 7 below:

Figure 7 – IPv6 Packet Fields  

Knowing what is in the IPv4 header is important from a network designer standpoint because many of the fields in the header are used for features such as QoS or protocol type. The IPv6 header offers additional functionality, even though some fields from the IPv4 header have been eliminated, such as the Fragment Offset field and the Flags field.

The Version field, as in the IPv4 header, offers information about the IP protocol version. The Traffic Class field is used to tag the packet with the class of traffic it uses in its DiffServ mechanisms. IPv6 also adds a Flow Label field, which can be used for QoS mechanisms, by tagging a flow. This can be used for multilayer switching techniques and will offer faster packet switching on the network devices. The Payload Length field is the same as the Total Length field in IPv4.

The Next Header is an important IPv6 field. The value of this field determines the type of information that follows the basic IPv6 header. It can be a Transport Layer packet like TCP or UDP or it can designate an extension header. The Next Header field is the equivalent of the Protocol field in IPv4. The next field is Hop Limit, which designates the maximum number of hops an IP packet can traverse. Each hop/router decrements this field by one, so this is similar to the TTL field in IPv4. There is no Checksum field in the IPv6 header , so the router can decrement the Hop Limit field without recalculating the checksum. Finally, there is the 128-bit source address and the 128-bit destination address.

In addition to these fields there are a number of extension headers. The extension headers and the data portion of the packet will follow the eight fields covered thus far. The total length of an extension header’s chain can be variable because the number of extension headers is not fixed. There are different types of extension headers, such as the following:

• Routing header
• Fragmentation header
• Authentication header
• IPsec ESP header
• Hop-by-Hop Options header

The IPv4 address is comprised of a string of 32 bits represented in four octets using a dotted decimal format. IPv6, on the other hand, is comprised of 128 bits represented in eight groups of 16 bits using a hexadecimal format (i.e., 16 bits separated by colons), for example:

2001:43aa:0000:0000:11b4:0031:0000:c110.

Considering the complex format of IPv6 addresses, some rules were developed to shorten them:

• One or more successive 16-bit groups that consist of all zeros can be omitted and represented by two colons (::).
• If a 16-bit group begins with one or more zeros, the leading zeros can be omitted.

Considering the IPv6 example above, here are its shortened representations:

2001:43aa::11b4:0031:0000:c110

2001:43aa::11b4:0031:0:c110

2001:43aa::11b4:31:0:c110

In a mixed IPv4 and IPv6 environment, the IPv4 address can be embedded in the IPv6 address, specifically in the last 32 bits.

The prefix portion in IPv6 is the number of contiguous bits that represent the network host. For example, the address 2001:0000:0000:0AABC:0000:0000:0000:0000/60 can be represented as 2001:0:0:ABC::/60.

Several types of IPv6 addresses are required for various applications. When compared to IPv4 address types (i.e., unicast, multicast, and broadcast), IPv6 presents some differences: special multicast addresses are used instead of broadcast addressing, and a new address type was defined called anycast.

Anycast addresses are generally assigned to servers located in different geographical locations. By connecting to the anycast address, users will reach the closest server. Anycast addresses are also called one-to-nearest addresses. The IPv6 multicast address is a one-to-many address that identifies a set of hosts that will receive the packet. This is similar to an IPv4 Class D multicast address . IPv6 multicast addresses also supersede the broadcast function of IPv4 broadcast. IPv6 broadcast functionality is an all-nodes multicast behavior. The following are well-known multicast addresses that should be remembered:

• FF01::1 = all-nodes multicast address (broadcast)
• FF02::2 = all-routers multicast address (used for link-local address mechanisms)

Another important multicast address is the solicited node multicast address, which is created automatically and placed on the interface. This is used by the IPv6 Neighbor Discovery process to improve upon IPv4 ARP. A special IPv6 address is 0:0:0:0:0:0:0:1, which is the IPv6 loopback address, equivalent to the 127.0.0.1 IPv4 loopback address. This can also be represented as ::1/128.

The link-local addresses are significant only to individual nodes on a single link. Routers forward packets with a link-local source or destination address beyond the local link. Link-local addresses can be configured automatically or manually. Global unicast addresses are globally unique and routable and are defined in RFC 2374 and RFC 3587.

Figure 8 – IPv6 Global Unicast Address Format

Based on the IPv6 global unicast address format shown in Figure 8 above, the first 23 bits represent the registry, the first 32 bits represent the ISP prefix, the first 48 bits are the site prefix, and /64 represents the subnet prefix. The remaining bits are allocated to the interface ID.

The global unicast address and the anycast address share the same format. The unicast address space actually allocates the anycast address. To devices that are not configured for anycast, these addresses will appear as unicast addresses.

IPv6 global unicast addressing allows aggregation upward to the ISP. A single interface may be assigned multiple addresses of any type (i.e., unicast, anycast, and multicast). However, every IPv6-enabled interface must have a loopback address and a link-local address.

The IPv6 global unicast address is structured as presented above in Figure 3.8 to facilitate aggregation and reduce its number in the global routing tables, just like with IPv4. Global unicast addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Typically, a global unicast address is made up of a 48-bit global routing prefix and a 16-bit subnet identifier.

IPv6 Mechanisms

As with IPv4, there are different mechanisms available for IPv6 and the most important of these includes the following:

• IPv6 Neighbor Discovery (ND)
• Name resolution
• Path Maximum Transmission Unit (MTU) Discovery
• IPv6 security
• IPv6 routing protocols

The Internet Control Message Protocol (ICMP) was modified to support IPv6 and is one of the most important mechanisms that support IPv6 functionality. ICMPv6 uses a Next Header number of 58. ICMP provides informational messages (e.g., Echo Request and Echo Reply) and error messages (e.g., Destination Unreachable, Packet Too Big, and Time Exceeded). IPv6 also uses ICMPv6 to determine important parameters, such as neighbor availability, Path MTU Discovery, destination addresses, or port reachability.

IPv6 uses a Neighbor Discovery protocol (RFC 2461), unlike IPv4, which uses the Address Resolution Protocol (ARP). IPv6 hosts use ND to implement “plug and play” functionality and to discover all other nodes on the same link. ND is also used in checking for duplicate addresses and finding the routers on a specific link. ND uses the ICMPv6 message structure in its operations and its type codes are 133 through 137:

• Router Solicitation
• Router Advertisement
• Neighbor Solicitation
• Neighbor Advertisement

Neighbor Discovery goes beyond the capabilities of ARP, as it performs many functions:

• Address Auto-Configuration (a host can find its full address without using DHCP)
• Duplicate Address Detection (DAD)
• Prefix Discovery (learns prefixes on local links)
• Link MTU Discovery
• Hop Count Discovery
• Next-Hop Determination
• Address Resolution
• Router Discovery (allows routers to find other local routers)
• Neighbor Reachability Detection
• Redirection
• Proxy Behavior
• Default Router Selection

Many of the features mentioned above have IPv4 equivalencies but some of them are unique to IPv6 and provide additional functionalities.

One of the important features made possible by the ND process is DAD, as defined in RFC 4862. This is accomplished through Neighbor Solicitation messages that are exchanged before the interface is allowed to use a global unicast address on the link, and this can determine whether the particular address is unique. The Target Address field in these specific packets is set to the IPv6 address for which duplication is being detected and the source address is set to unspecified (::).

The IPv6 stateless Auto-Configuration feature avoids using DHCP to maintain a mapping for the address assignment. This is a very low-overhead manner in which to disseminate addresses and it accommodates low-overhead re-addressing. In this process, the router sends a Router Advertisement message to advertise the prefix and its ability to act as a default gateway. The host receives this information and uses the EUI-64 format to generate the host portion of the address. After the host generates the address, it starts the DAD process to ensure that the address is unique on the network.

IPv4 performs Name Resolution by using A records in the DNS. RFC 3596 offers a new DNS record type to support the transition to IPv6 Name Resolution, which is AAAA (Quad A). The Quad A record will return an IPv6 address based on a given domain name.

IPv6 does not allow packet fragmentation through the network (except for the source of the packet), so the MTU of every link in an IPv6 implementation must be 1280 bytes or greater. The ICMPv6 Packet Too Big error message determines the path MTU because nodes along the path will send this message to the sending hosts if the packet is larger than the outgoing interface MTU.

DHCPv6 is an updated version of DHCP that offers dynamic address assignment for version 6 hosts. DHCPv6 is described in RD 3315 and provides the same functionality as DHCP but it offers more control, as it supports renumbering without numbers.

IPv6 also has some security mechanisms. Unlike IPv4, IPv6 natively supports IPsec (an open security framework) with two mechanisms: the Authentication Header (AH) and the Encapsulating Security Payload (ESP).

The support for IPsec in IPv6 is mandatory, unlike with IPv4. By making it mandatory in all the IPv6 nodes, secure communication can be created with any node in the network. An example of mandatory and leveraged IPsec in IPv6 is OSPF, which carries out its authentication using only IPsec. Another example of the IPsec IPv6 mechanism is the IPsec Site-to-Site Virtual Tunnel Interface, which allows easy creation of virtual tunnels between two IPv6 routers to very quickly form a site-to-site secured Virtual Private Network (VPN).

The following new routing protocols were developed for IPv6:

• RIPng (RIP new generation)
• Integrated Intermediate System-to-Intermediate System Protocol (IS-IS)
• EIGRP for IPv6
• BGP4 multiprotocol extensions for IPv6

Transitioning from IPv4 to IPv6

Because IPv6 almost always comes as an upgrade to the existing IPv4 infrastructure, IPv6 network design and implementation considerations must include different transition mechanisms between these two protocol suites. The IPv4 to IPv6 transition can be very challenging, and during the transition period it is very likely that both protocols will coexist on the network .

The designers of the IPv6 protocol suite have suggested that IPv4 will not go away anytime soon, and it will strongly coexist with IPv6 in combined addressing schemes. The key to all IPv4 to IPv6 transition mechanisms is dual-stack functionality, which allows a device to operate both in IPv4 mode and in IPv6 mode.

One of the most important IPv4 to IPv6 transition mechanisms involves tunneling between dual-stack devices and this can be implemented in different flavors:

• Generic Routing Encapsulation (GRE) – default tunnel mode
• IPv6IP (less overhead, no CLNS transport)
• 6to4 (embeds IPv4 address into IPv6 prefix to provide automatic tunnel endpoint determination); automatically generates tunnels based on the utilized addressing scheme
• Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) – automatic host-to-router and host-to-host tunneling

Figure 9 – IPv6 over IPv4 Tunneling

Analyzing Figure 9 above, the IPv4 island contains two dual-stack routers that run both the IPv4 and the IPv6 protocol stacks. These two routers will be able to support the transition mechanisms by tunneling IPv6 inside IPv4, and the two routers each connect to an IPv6 island. To carry IPv6 traffic between the two edge islands, a tunnel is created between the two routers that encapsulate IPv6 packets inside IPv4 packets. These packets are sent through the IPv4 cloud as regular IPv4 packets and they get de-encapsulated when they reach the other end. An IPv6 packet generated in the left-side network reaches a destination in the right-side network, so it is very easy to tunnel IPv6 inside IPv4 because of the dual-stack routers at the edge of the IPv4 infrastructure. Static tunneling methods are generally used when dealing with point-to-point links, while dynamic tunneling methods work best when using point-to-multipoint connections.

Network Address Translation Protocol Translation (NAT-PT) is another technology that can be utilized to carry out the transition to an IPv6 network. NAT-PT is often confused with NAT but it is a completely different technology. Simple NAT can also be used in IPv6 but this is very rare because IPv6 offers a very large address space and private addresses are not necessary. NAT-PT is another translation mechanism that will dynamically convert IPv4 addresses to IPv6 addresses, and vice-versa.

Another static tunneling technology is IPv6IP, which encapsulates IPv4 packets directly into IPv6. This is also called manual tunneling. Another type of static tunnel that can be created is a GRE tunnel that encapsulates the IPv6 packets within a GRE packet. GRE tunneling might be necessary when using special applications and services, like the IS-IS routing protocol for IPv6.

The dynamic tunnel types include the 6to4 tunnel, which is appropriate when a group of destinations needs to be connected dynamically utilizing IPv6. ISATAP is a unique type of host-to-router dynamic tunnel, unlike the previously mentioned tunneling techniques, which are router-to-router. ISATAP allows hosts to dynamically get to their IPv6 default gateway.

IPv6 Compared to IPv4

A network designer should have a very clear picture of the advantages IPv6 has over IPv4. The enhancements of IPv6 can be summarized as follows:

• IPv6 uses hexadecimal notation instead of dotted-decimal notation (IPv4).
• IPv6 has an expanded address space, from 32 bits to 128 bits .
• IPv6 addresses are globally unique due to the extended address space, eliminating the need for NAT.
• IPv6 has a fixed header length (40 bytes), allowing vendors to improve switching efficiency.
• IPv6 supports enhanced options (that offer new features) by placing extension headers between the IPv6 header and the Transport Layer header.
• IPv6 offers Address Auto-Configuration, providing for the dynamic assignment of IP addresses even without a DHCP server.
• IPv6 offers support for labeling traffic flows.
• IPv6 has security capabilities built-in, including authentication and privacy via IPsec
• IPv6 offers Path MTU Discovery before sending packets to a destination, eliminating the need for fragmentation.
• IPv6 supports site multi-homing.
• IPv6 uses the ND protocol instead of ARP.
• IPv6 uses AAAA DNS records instead of A records (IPv4).
• IPv6 uses site-local addressing instead of RFC 1918 (IPv4).
• IPv4 and IPv6 use different routing protocols.
• IPv6 provides for anycast addressing.

You can learn more about network design for security and wireless in our Cisco CCNP Encor course here .

Good IP addressing for network design uses summarizable blocks of addresses that enable route summarization and provide a number of benefits:

• Reduced router workload and routing traffic
• Increased network stability
• Significantly simplified troubleshooting

Creating and using summary routes depends on the use of summarizable blocks of addresses . Sequential numbers in an octet may denote a block of IP addresses as summarizable. For sequential numbers to be summarizable, the block must be X numbers in a row, where X is a power of 2, and the first number in the sequence must be a multiple of X. The created sequence will then end one before the next multiple of X in all cases.

Efficiently assigning IP addresses to the network is a critical network design decision, impacting the scalability of the network and the routing protocols that can be used. IPv4 addressing has the following characteristics:

• IPv4 addresses are 32 bits in length.
• IPv4 addresses are divided into various classes (e.g., Class A networks accommodate more than 16 million unique IP addresses, Class B networks support more than 65 thousand IP addresses, and Class C networks permit 254 usable IP addresses). Originally, organizations applied for an entire network in one of these classes. Today, however, subnetting allows an ISP to give a customer just a portion of a network’s address space, in an attempt to conserve the depleting pool of IP addresses. Conversely, ISPs can use supernetting (also known as Classless Inter-Domain Routing – CIDR) to aggregate the multiple network address spaces that they have. Aggregating multiple network address spaces into one address reduces the amount of route entries a router must maintain.
• Devices such as PCs can be assigned a static IP address, by hard coding the IP address in the device’s configuration. Alternatively, devices can dynamically obtain an address from a DHCP server , for example.
• Because names are easier to remember than IP addresses are, most publicly accessible Web resources are reachable by their name. However, routers must determine the IP address with which the name is associated to route traffic to that destination. Therefore, a DNS server can perform the translation between domain names and their corresponding IP addresses.
• Some IP addresses are routable through the public Internet, whereas other IP addresses are considered private and are intended for use within an organization. Because these private IP addresses might need to communicate outside the LAN, NAT can translate a private IP address into a public IP address. In fact, multiple private IP addresses can be represented by a single public IP address using NAT. This type of NAT is called Port Address Translation (PAT) because the various communication flows are identified by the port numbers they use to communicate with outside resources.

When beginning to design IP addressing for a network, the following aspects must be determined:

• The number of network locations that need IP addressing
• The number of devices requiring an IP address at each location
• Customer-specific IP addressing requirements (e.g., static IP addressing versus dynamic IP addressing)
• The number of IP addresses that need to be contained in each subnet (e.g., a 48-port switch in a wiring closet might belong to a subnet that supports 64 IP addresses)

A major challenge with IPv4 is the limited number of available addresses . A newer version of IP, specifically IPv6, addresses this concern. An IPv6 address is 128 bits long, compared to the 32-bit length of an IPv4 address.

To make such a large address more readable, an IPv6 address uses hexadecimal numbers and the 128-bit address is divided into eight fields. Each field is separated by a colon, as opposed to the four fields in an IPv4 address, which are each separated by a period. To further reduce the complexity of the IPv6 address, leading 0s in a field are optional and if one or more consecutive fields contain all 0s, those fields can be represented by a double colon (::). A double colon can be used only once in an address; otherwise, it would be impossible to know how many 0s are present between each pair of colons.

Consider some of the benefits offered by IPv6:

• IPv6 dramatically increases the number of available addresses.
• Hosts can have multiple IPv6 addresses, allowing those hosts to multi-home to multiple ISPs.
• Other benefits include enhancements relating to QoS, security, mobility, and multicast technologies.

Unlike IPv4, IPv6 does not use broadcasts. Instead, IPv6 uses the following methods for sending traffic from a source to one or more destinations:

• Unicast (one-to-one): Unicast support in IPv6 allows a single source to send traffic to a single destination, just as unicast functions in IPv4.
• Anycast (one-to-nearest): A group of interfaces belonging to nodes with similar characteristics (e.g., interfaces in replicated FTP servers) can be assigned an anycast address. When a host wants to reach one of those nodes, the host can send traffic to the anycast address and the node belonging to the anycast group that is closest to the sender will respond.
• Multicast (one-to-many): Like IPv4, IPv6 supports multicast addressing, where multiple nodes can join a multicast group. The sender sends traffic to the multicast IP address and all members of the multicast group receive the traffic.

The migration of an IPv4 network to an IPv6 network can take years because of the expenditures of upgrading equipment. Therefore, during the transition, IPv4-speaking devices and IPv6-speaking devices need to coexist on the same network. Consider the following solutions for maintaining both IPv4 and IPv6 devices in the network:

• Dual stack: Some systems (including Cisco routers) can simultaneously run both IPv4 and IPv6, allowing communication to both IPv4 and IPv6 devices.
• Tunneling: To send an IPv6 packet across a network that uses only IPv4, the IPv6 packet can be encapsulated and tunneled through the IPv4 network.
• Translation: A device, such as a Cisco router, could sit between an IPv4 network and an IPv6 network and translate between the two addressing formats.

IPv6 allows the use of static routing and supports specific dynamic routing protocols that are variations of the IPv4 routing protocols modified or redesigned to support IPv6:

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How-To Geek

How do ip addresses work.

Every device connected to a network---computer, tablet, camera, whatever---needs a unique identifier so that other devices know how to reach it.

Quick Links

What is an ip address, what's the difference between ipv4 and ipv6, how does a device get its ip address.

Every device connected to a network---computer, tablet, camera, whatever---needs a unique identifier so that other devices know how to reach it. In the world of TCP/IP networking, that identifier is the Internet Protocol (IP) address.

If you've worked with computers for any amount of time, you've likely been exposed to IP addresses---those numerical sequences that look something like 192.168.0.15. Most of the time, we don't have to deal with them directly, since our devices and networks take care of that stuff behind the scenes. When we do have to deal with them, we often just follow instructions about what numbers to put where. But, if you've ever wanted to dive a little deeper into what those numbers mean, this article is for you.

Related: 8 Common Network Utilities Explained

Why should you care? Well, understanding how IP addresses work is vital if you ever want to troubleshoot why your network isn't working right , or why a particular device isn't connecting the way you'd expect it to. And, if you ever need to set up something a little more advanced---like hosting a game server or media server to which friends from the internet can connect---you'll need to know something about IP addressing. Plus, it's kind of fascinating.

Note: We're going to be covering the basics of IP addressing in this article, the kind of stuff that people who use IP addresses, but never really thought much about them, might want to know. We're not going to be covering some of the more advanced, or professional, level stuff, like IP classes, classless routing, and custom subnetting...but we will point to some sources for further reading as we go along.

An IP address uniquely identifies a device on a network. You've seen these addresses before; they look something like 192.168.1.34.

An IP address is always a set of four numbers like that. Each number can range from 0 to 255. So, the full IP addressing range goes from 0.0.0.0 to 255.255.255.255.

The reason each number can only reach up to 255 is that each of the numbers is really an eight digit binary number (sometimes called an octet). In an octet, the number zero would be 00000000, while the number 255 would be 11111111, the maximum number the octet can reach. That IP address we mentioned before (192.168.1.34) in binary would look like this: 11000000.10101000.00000001.00100010.

Computers work with the binary format, but we humans find it much easier to work with the decimal format. Still, knowing that the addresses are actually binary numbers will help us understand why some things surrounding IP addresses work the way they do.

Don't worry, though! We're not going to be throwing a lot of binary or math at you in this article, so just bear with us a bit longer.

The Two Parts of An IP Address

A device's IP address actually consists of two separate parts:

• Network ID: The network ID is a part of the IP address starting from the left that identifies the specific network on which the device is located. On a typical home network, where a device has the IP address 192.168.1.34, the 192.168.1 part of the address will be the network ID. It's custom to fill in the missing final part with a zero, so we might say that the network ID of the device is 192.168.1.0.
• Host ID: The host ID is the part of the IP address not taken up by the network ID. It identifies a specific device (in the TCP/IP world, we call devices "hosts") on that network. Continuing our example of the IP address 192.168.1.34, the host ID would be 34---the host's unique ID on the 192.168.1.0 network.

On your home network, then, you might see several devices with IP address like 192.168.1.1, 192.168.1.2, 192.168.1 30, and 192.168.1.34. All of these are unique devices (with host IDs 1, 2, 30, and 34 in this case) on the same network (with the network ID 192.168.1.0).

To picture all this a little better, let's turn to an analogy. It's pretty similar to how street addresses work within a city. Take an address like 2013 Paradise Street. The street name is like the network ID, and the house number is like the host ID. Within a city, no two streets will be named the same, just like no two network IDs on the same network will be named the same. On a particular street, every house number is unique, just like all host iDs within a particular network ID are unique.

The Subnet Mask

So, how does your device determine which part of the IP address is the network ID and which part the host ID? For that, they use a second number that you'll always see in association with an IP address. That number is called the subnet mask.

On most simple networks (like the ones in homes or small businesses), you'll see subnet masks like 255.255.255.0, where all four numbers are either 255 or 0. The position of the changes from 255 to 0 indicate the division between the network and host ID. The 255s "mask out" the network ID from the equation.

Note: The basic subnet masks we're describing here are known as default subnet masks. Things get more complicated than this on bigger networks. People often use custom subnet masks (where the position of the break between zeros and ones shifts within an octet) to create multiple subnets on the same network. That's a little beyond the scope of this article, but if you're interested, Cisco has a pretty good guide on subnetting .

The Default Gateway Address

Related: Understanding Routers, Switches, and Network Hardware

In addition to the IP address itself and the associated subnet mask, you'll also see a default gateway address listed along with IP addressing information. Depending on the platform you're using, this address might be called something different. It's sometimes called the "router," "router address," default route," or just "gateway." These are all the same thing. It's the default IP address to which a device sends network data when that data is intended to go to a different network (one with a different network ID) than the one the device is on.

The simplest example of this is found in a typical home network.

If you have a home network with multiple devices, you likely have a router that's connected to the internet through a modem. That router might be a separate device, or it might be part of a modem/router combo unit supplied by your internet provider. The router sits between the computers and devices on your network and the more public-facing devices on the internet, passing (or routing) traffic back and forth.

Say you fire up your browser and head to www.howtogeek.com. Your computer sends a request to our site's IP address. Since our servers are on the internet rather than on your home network, that traffic is sent from your  PC to your router (the gateway), and your router forwards the request on to our server. The server sends the right information back to your router, which then routes the information back to the device that requested it, and you see our site pop up in your browser.

Typically, routers are configured by default to have their private IP address (their address on the local network) as the first host ID. So, for example, on a home network that uses 192.168.1.0 for a network ID, the router is usually going to be 192.168.1.1. Of course, like most things, you can configure that to be something different if you want.

Related: How to Find Your Router's IP Address on Any Computer, Smartphone, or Tablet

DNS Servers

There's one final piece of information you'll see assigned alongside a device's IP address, subnet mask, and default gateway address: the addresses of one or two default Domain Name System (DNS) servers. We humans work much better with names than numerical addresses. Typing www.howtogeek.com into your browser's address bar is much easier than remembering and typing our site's IP address.

DNS works kind of like a phone book, looking up human-readable things like website names, and converting those to IP addresses. DNS does this by storing all that information on a system of linked DNS servers across the internet. Your devices need to know the addresses of DNS servers to which to send their queries.

Related: What Is DNS, and Should I Use Another DNS Server?

On a typical small or home network, the DNS server IP addresses are often the same as the default gateway address. Devices send their DNS queries to your router, which then forwards the requests on to whatever DNS servers the router is configured to use. By default, these are usually whatever DNS servers your ISP provides, but you can change those to use different DNS servers if you want. Sometimes, you might have better success using DNS servers provided by third parties , like Google or OpenDNS.

You also may have noticed while browsing through settings a different type of IP address, called an IPv6 address. The types of IP addresses we've talked about so far are addresses used by IP version 4 (IPv4)---a protocol developed in the late 70s. They use the 32 binary bits we talked about (in four octets) to provide a total of 4.29 billion possible unique addresses. While that sounds like a lot, all the publicly available addresses were long ago assigned to businesses. Many of them are unused, but they are assigned and unavailable for general use.

In the mid-90s, worried about the potential shortage of IP addresses, the internet Engineering Task Force (IETF) designed IPv6. IPv6 uses a 128-bit address instead of the 32-bit address of IPv4, so the total number of unique addresses is measured in the undecillions---a number big enough that it's unlikely to ever run out.

Unlike the dotted decimal notation used in IPv4, IPv6 addresses are expressed as eight number groups, divided by colons. Each group has four hexadecimal digits that represents 16 binary digits (so, it's referred to as a hextet). A typical IPv6 address might look something like this:

2601:7c1:100:ef69:b5ed:ed57:dbc0:2c1e

The thing is, the shortage of IPv4 addresses that caused all the concern ended up being mitigated to a large extent by the increased use of private IP addresses behind routers. More and more people created their own private networks, using those private IP addresses that aren't exposed publicly.

So, even though IPv6 is still a major player and that transition will still happen, it never happened as fully as predicted---at least not yet. If you're interested in learning more, check out this history and timeline of IPv6 .

Now that you know the basics of how IP addresses work, let's talk about how devices get their IP addresses in the first place. There are really two types of IP assignments: dynamic and static.

Related: How to Find Any Device's IP Address, MAC Address, and Other Network Connection Details

A dynamic IP address is assigned automatically when a device connects to a network. The vast majority of networks today (including your home network) use something called Dynamic Host Configuration Protocol (DHCP) to make this happen. DHCP is built into your router. When a device connects to the network, it sends out a broadcast message requesting an IP address. DHCP intercepts this message, and then assigns an IP address to that device from a pool of available IP addresses.

There are certain private IP address ranges  routers will use for this purpose. Which is used depends on who made your router, or how you have set things up yourself. Those private IP ranges include:

• 10.0.0.0 - 10.255.255.255: If you're a Comcast/Xfinity customer, the router provided by your ISP assigns addresses in this range. Some other ISPs also use these addresses on their routers, as does Apple on their AirPort routers.
• 192.168.0.0 - 192.168.255.255: Most commercial routers are set up to assign IP addresses in this range. For example, most Linksys routers use the 192.168.1.0 network, while D-Link and Netgear both use the 198.168.0.0 range
• 172.16.0.0 - 172.16.255.255: This range is rarely used by any commercial vendors by default.
• 169.254.0.0 - 169.254.255.255: This is a special range used by a protocol named Automatic Private IP Addressing. If your computer (or other device) is set up to retrieve its IP address automatically, but cannot find a DHCP server, it assigns itself an address in this range. If you see one of these addresses, it tells you that your device could not reach the DHCP server when it came time to get an IP address, and you may have a networking issue or trouble with your router.

The thing about dynamic addresses is that they can sometimes change. DHCP servers lease IP addresses to devices, and when those leases are up, the devices must renew the lease. Sometimes, devices will get a different IP address from the pool of addresses the server can assign.

Most of the time, this is not a big deal, and everything will "just work". Occasionally, however, you might want to give a device an IP address that does not change. For example, maybe you have a device that you need to access manually, and you find it easier to remember an IP address than a name. Or maybe you have certain apps that can only connect to network devices using their IP address.

In those cases, you can assign a static IP address to those devices. There are a couple of ways to do this. You can  manually configure the device with a static IP address yourself, although this can sometimes be janky. The other, more elegant solution is to configure your router to assign static IP addresses to certain devices during what would normally be dynamic assignment by the DHCP server. That way, the IP address never changes, but you don't interrupt the DHCP process that keeps everything working smoothly.

IPv6 Address Assignment Example

Lesson Contents

In this lesson we’ll take a look how you can create IPv6 prefixes and subnets so that you can configure your entire network with IPv6. We’ll start at the top where IANA (Internet Assigned Numbers Authority) is responsible for the global coordination of the IPv4 and IPv6 address space and move our way all the way to the bottom where we assign subnets and IPv6 addresses to our routers, switches and VLANs.

IPv6 Global Unicast Prefix Assignments

IANA “owns” the entire IPv6 address space and they assign certain prefixes to the RIRs (Regional Internet Registry). There are 5 RIRs at the moment:

• AFRINIC : Africa
• APNIC : Asia/Pacific
• ARIN : North America
• LACNIC : Latin America and some Caribbean Islands
• RIPE NCC : Europe, Middle east and Central Asia

If you are interested, click here for an overview of all IPv6 prefix assignments by IANA.

When a large ISP (or large company) in North America wants IPv6 addresses then they will contact ARIN who will assign them an IPv6 prefix if they meet all requirements. The ISP can then assign prefixes to their customers.

Let’s take a look at some actual prefixes:

• IANA is using the 2000::/3 prefix for global unicast address space.
• According to this list, RIPE NCC received prefix 2001:4000::/23 from IANA.
• A large ISP called Ziggo in The Netherlands receives prefix 2001:41f0::/32 from RIPE NCC.
• The ISP assigns prefix 2001:41f0:4060::/48 to one of their customers.

Now it’s up to the customer what they want to do with their IPv6 prefix…

IPv6 Global Unicast Subnet Assignments

Our customer received prefix 2001:41f0:4060::/48 and they want to use it to configure IPv6 on their entire network. Where do we start? Take a look at the image below:

The 48-bit prefix that we received is typically called the global routing prefix or site prefix . The interface ID is normally 64 bit which means we have 16 bits left to create subnets .

If I want I can steal some more bits from the Interface ID to create even more subnets but there’s no need for this. Using 16 bits we can create 65.536 subnets …more than enough for most of us. Let’s see what we can do for our customer:

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Rene, just to be clear, they aren’t the same right? 2001:41f0:4060:10::/64 and 2001:41f0:4060:A::/64 ?

That’s right.

shouldn’t this be /64 ?

Yes that’s right, just fixed it. Thanks!

Why are these not the same

2001:41f0:4060:10::/64 and 2001:41f0:4060:A::/64 ?

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IP Subnet Calculator

This calculator returns a variety of information regarding Internet Protocol version 4 (IPv4) and IPv6 subnets including possible network addresses, usable host ranges, subnet mask, and IP class, among others.

IPv4 Subnet Calculator

Ipv6 subnet calculator.

Related Bandwidth Calculator | Binary Calculator

A subnet is a division of an IP network (internet protocol suite), where an IP network is a set of communications protocols used on the Internet and other similar networks. It is commonly known as TCP/IP (Transmission Control Protocol/Internet Protocol).

The act of dividing a network into at least two separate networks is called subnetting, and routers are devices that allow traffic exchange between subnetworks, serving as a physical boundary. IPv4 is the most common network addressing architecture used, though the use of IPv6 has been growing since 2006.

An IP address is comprised of a network number (routing prefix) and a rest field (host identifier). A rest field is an identifier that is specific to a given host or network interface. A routing prefix is often expressed using Classless Inter-Domain Routing (CIDR) notation for both IPv4 and IPv6. CIDR is a method used to create unique identifiers for networks, as well as individual devices. For IPv4, networks can also be characterized using a subnet mask, which is sometimes expressed in dot-decimal notation, as shown in the "Subnet" field in the calculator. All hosts on a subnetwork have the same network prefix, unlike the host identifier, which is a unique local identification. In IPv4, these subnet masks are used to differentiate the network number and host identifier. In IPv6, the network prefix performs a similar function as the subnet mask in IPv4, with the prefix length representing the number of bits in the address.

Prior to the introduction of CIDR, IPv4 network prefixes could be directly obtained from the IP address based on the class (A, B, or C, which vary based on the range of IP addresses they include) of the address and the network mask. Since the introduction of CIDRs, however, assigning an IP address to a network interface requires both an address and its network mask.

Below is a table providing typical subnets for IPv4.

Ipconfig Configure Static IP Address in Windows 11: A Step-by-Step Guide

Setting up a static IP address on your Windows 11 computer is like giving your device a permanent home address on the internet. This can be useful if you want to set up a server, remote access, or just ensure a consistent connection. To do this, you’ll dive into the network settings, enter some numbers, and save your changes.

Step by Step Tutorial to Configure Static IP Address in Windows 11

Before we jump into the nitty-gritty, here’s a quick primer on what you’ll be doing: you’ll access the network settings, select your connection, and manually input IP information to replace the automatic settings.

Step 1: Open Network Settings

Open your Windows 11 settings and go to the network section.

Network settings are the control center for all things internet on your computer. By accessing these settings, you’re taking the first step towards customizing how your device connects to the world wide web.

Step 2: Edit IP Assignment

Find and click on the ‘Edit’ button under IP assignment.

This is where you’ll switch from having your IP address automatically assigned (usually by your router) to entering your own fixed numbers.

Step 3: Select Manual

In the edit network screen, select ‘Manual’ from the dropdown menu.

By selecting manual, you’re telling your computer that you’re the boss and you’ll be providing the IP address details.

Step 4: Enter IP Information

Enter the static IP address, subnet mask, and default gateway information.

This is the most technical part. You’ll need to know the right numbers to put here. They’ll typically come from your internet service provider or network administrator.

Step 5: Save Changes

Save your changes and exit the settings.

Once you’ve entered all the right numbers and double-checked them, hit save, and you’ve successfully set up a static IP address!

After you complete these steps, your Windows 11 machine will use the static IP address you’ve set. This means that every time your device connects to the network, it will use the same IP address, which can help in various networking scenarios.

Tips for Configuring Static IP Address in Windows 11

• Ensure you have the correct IP address, subnet mask, default gateway, and DNS server information before starting.
• Always double-check the numbers you enter to avoid connectivity issues.
• If you’re not sure what numbers to use, consult your internet service provider or network administrator.
• Remember that setting a static IP address might cause conflicts if other devices are using the same address; make sure it’s unique within your network.
• If you encounter connectivity problems after setting a static IP address, you can always switch back to automatic IP assignment.

Frequently Asked Questions

What is a static ip address.

A static IP address is a fixed address assigned to your computer that doesn’t change over time.

Why would I want to set a static IP address?

You might want a static IP if you’re setting up a server, need remote access, or want a consistent connection without the risk of your IP changing.

Will setting a static IP address make my internet faster?

Not necessarily. It’s more about consistency and control than speed.

Can I set a static IP address on a Wi-Fi connection?

Yes, you can set it on any type of network connection, including Wi-Fi.

What if I set the wrong static IP address?

If you enter incorrect information, you might lose your internet connection. Double-check your numbers or revert to automatic assignment to fix this.

• Open Network Settings
• Edit IP Assignment
• Select Manual
• Enter IP Information
• Save Changes

Configuring a static IP address in Windows 11 is a straightforward process that can bring several benefits to your network management. Whether you’re a gamer wanting to host uninterrupted gaming sessions, a professional needing stable remote access, or just someone keen on organizing their network, a static IP address is a way to go. Remember to always have the right information on hand before you start, and don’t hesitate to seek help if you’re unsure about the numbers you need to input. With the steps provided, you’re well on your way to a more stable and predictable network experience. Keep in mind that while static IP addresses have many advantages, they may not be necessary for everyone. Assess your needs, do your homework, and if it all adds up, take the plunge and give your Windows 11 device that permanent spot on the digital map.

Matthew Burleigh has been writing tech tutorials since 2008. His writing has appeared on dozens of different websites and been read over 50 million times.

After receiving his Bachelor’s and Master’s degrees in Computer Science he spent several years working in IT management for small businesses. However, he now works full time writing content online and creating websites.

His main writing topics include iPhones, Microsoft Office, Google Apps, Android, and Photoshop, but he has also written about many other tech topics as well.

Read his full bio here.

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How To Get A Network Switch To Assign IP

• Internet & Connectivity
• WiFi & Ethernet

Introduction

Understanding the basics of network switches and ip address assignment.

Network switches play a vital role in the functioning of computer networks, serving as the central point for connecting devices and facilitating the seamless transfer of data. When it comes to assigning IP addresses within a network, network switches are essential components that enable efficient communication between devices. In this article, we will delve into the fundamental concepts of network switches and explore the process of configuring and assigning IP addresses to devices connected to the switch.

The process of assigning IP addresses to devices connected to a network switch is crucial for enabling effective communication and data transfer. Understanding the intricacies of network switches and IP address assignment is essential for network administrators, IT professionals, and individuals seeking to optimize network performance.

Network switches are hardware devices that operate at the data link layer of the OSI model, facilitating the transfer of data between devices within a local area network (LAN). Unlike hubs, which simply broadcast data to all connected devices, switches intelligently forward data packets only to the intended recipient, thereby optimizing network efficiency and reducing unnecessary network traffic.

In the context of IP address assignment, a network switch serves as a central point through which devices can be interconnected and assigned unique IP addresses. This process is fundamental for enabling devices to communicate with each other and access network resources effectively.

Throughout this article, we will explore the various aspects of network switches and delve into the configuration and assignment of IP addresses, providing a comprehensive guide for network administrators and individuals seeking to gain a deeper understanding of these critical networking components. Let's embark on this journey to unravel the intricacies of network switches and the process of assigning IP addresses within a network.

Understanding Network Switches

Network switches are integral components of modern computer networks, playing a pivotal role in facilitating efficient data transfer and communication among connected devices. These devices operate at the data link layer of the OSI model, enabling the seamless exchange of data within a local area network (LAN).

Unlike traditional hubs that indiscriminately broadcast data to all connected devices, network switches utilize a method known as packet switching to intelligently forward data packets only to the intended recipients. This dynamic routing of data enhances network efficiency by reducing unnecessary traffic and optimizing data transfer speeds.

One of the key advantages of network switches is their ability to create dedicated communication channels between devices, thereby minimizing data collisions and congestion within the network. By establishing individual communication paths, switches enable devices to transmit and receive data simultaneously, enhancing network performance and overall throughput.

Modern network switches often incorporate advanced features such as VLAN (Virtual Local Area Network) support, Quality of Service (QoS) capabilities, and Power over Ethernet (PoE) functionality. VLAN support allows for the segmentation of a single physical network into multiple virtual networks, enhancing security and network management. QoS features enable the prioritization of specific types of network traffic, ensuring optimal performance for critical applications and services. Additionally, PoE functionality empowers switches to deliver power to connected devices such as IP phones, wireless access points, and surveillance cameras over the Ethernet cable , eliminating the need for separate power sources.

Understanding the various types of network switches, including unmanaged, managed, and layer 3 switches, is essential for network administrators and IT professionals. Unmanaged switches are plug-and-play devices that operate without the need for configuration, making them suitable for small-scale deployments. In contrast, managed switches offer greater flexibility and control, allowing for advanced configuration, monitoring, and optimization of network performance. Layer 3 switches, also known as multilayer switches, possess routing capabilities and can make forwarding decisions based on IP addresses, enhancing network scalability and efficiency.

By comprehending the functionalities and capabilities of network switches, individuals can harness the full potential of these critical networking components to build robust and high-performing computer networks.

Configuring the Network Switch

Configuring a network switch is a fundamental aspect of network administration, enabling administrators to optimize network performance, enhance security, and ensure seamless connectivity among devices. Whether deploying a new switch or reconfiguring an existing one, the configuration process involves several key steps to tailor the switch’s settings to the specific requirements of the network.

1. Accessing the Switch: Before initiating the configuration process, it is essential to access the switch’s management interface. This can typically be achieved through a web-based interface or a command-line interface (CLI) using protocols such as HTTP, HTTPS, Telnet, or SSH. Access credentials, including usernames and passwords, are required to log in and begin the configuration process.

2. Initial Setup: Upon accessing the switch, the initial setup involves configuring basic settings such as the switch’s hostname, management IP address, subnet mask, and default gateway. These parameters are essential for enabling remote management and facilitating communication with other devices within the network.

3. VLAN Configuration: For managed switches, configuring Virtual Local Area Networks (VLANs) is a critical step in network segmentation and resource isolation. VLAN configuration involves creating, assigning ports to, and defining the characteristics of individual VLANs to optimize network security and performance.

4. Port Configuration: Each port on the network switch can be customized to accommodate specific network requirements. Administrators can configure port settings such as speed, duplex mode, and flow control to ensure optimal connectivity and data transfer rates based on the connected devices’ capabilities.

5. Quality of Service (QoS) Settings: Implementing QoS settings enables administrators to prioritize network traffic based on predefined rules, ensuring that critical applications receive the necessary bandwidth and network resources. QoS configuration is particularly beneficial for optimizing the performance of voice, video, and data-intensive applications within the network.

6. Security Configuration: Enhancing network security is paramount in the configuration process. This involves implementing measures such as port security, MAC address filtering, and IEEE 802.1X authentication to mitigate unauthorized access and safeguard the network against potential threats.

7. Firmware Updates and Backup: Regular firmware updates and configuration backups are essential for maintaining the switch’s stability and security. Administrators should ensure that the switch’s firmware is up to date and create backups of the configuration settings to facilitate swift recovery in the event of a system failure or configuration loss.

By meticulously configuring network switches to align with the specific requirements and security policies of the network, administrators can establish a robust and reliable network infrastructure capable of meeting the organization’s communication and data transfer needs.

Assigning IP Addresses

Assigning IP addresses to devices within a network is a critical process that enables seamless communication and data transfer. Network switches play a pivotal role in facilitating the assignment of unique IP addresses to connected devices, ensuring efficient network operation and resource accessibility.

1. DHCP Configuration: Dynamic Host Configuration Protocol (DHCP) is a commonly used method for automatically assigning IP addresses to devices within a network. When a device connects to the network, the DHCP server, often integrated into the network switch or managed by a dedicated server, dynamically allocates an IP address from a predefined pool, along with essential network configuration parameters such as subnet mask, default gateway, and DNS servers. DHCP simplifies the IP address assignment process, eliminating the need for manual configuration and minimizing the risk of address conflicts.

2. Static IP Address Assignment: In certain scenarios, static IP address assignment may be preferred for specific devices within the network. Network administrators can manually assign static IP addresses to devices, ensuring that each device retains a consistent and predefined IP address. This approach is beneficial for devices that necessitate fixed addressing, such as servers, network printers, and network-attached storage (NAS) devices.

3. Subnetting and IP Address Range Management: When assigning IP addresses, understanding subnetting principles and effectively managing IP address ranges is crucial. Subnetting allows for the segmentation of a larger network into smaller, more manageable subnetworks, optimizing network performance and resource allocation. By carefully managing IP address ranges and subnet configurations, administrators can efficiently utilize available IP addresses and minimize potential address conflicts.

4. IPv6 Address Assignment: With the proliferation of Internet of Things (IoT) devices and the exhaustion of IPv4 addresses, the adoption of IPv6 has become increasingly prevalent. Network switches must support IPv6 address assignment to accommodate the growing number of devices requiring unique IP addresses. IPv6 address assignment involves configuring devices with globally routable IPv6 addresses, ensuring seamless connectivity and future-proofing the network infrastructure.

5. Quality of Service (QoS) for IP Address Assignment: Implementing QoS policies for IP address assignment processes can optimize network performance and resource allocation. By prioritizing DHCP traffic and IP address assignment requests, administrators can ensure that devices connecting to the network receive timely and efficient IP address assignments, minimizing potential delays and enhancing overall user experience.

By leveraging the capabilities of network switches and employing best practices for IP address assignment, administrators can establish a robust and scalable network infrastructure capable of accommodating diverse devices and applications while facilitating seamless communication and data exchange.

Verifying IP Assignments

After the process of IP address assignment, it is essential to verify the successful allocation and configuration of IP addresses to connected devices within the network. This verification process ensures that devices can communicate effectively, access network resources, and operate without connectivity issues.

1. Network Discovery Tools: Utilizing network discovery tools such as ping, traceroute, and network scanning utilities allows administrators to verify the connectivity and reachability of devices within the network. By pinging assigned IP addresses and conducting traceroute analyses, administrators can confirm the responsiveness and accessibility of devices, ensuring seamless communication across the network.

2. DHCP Lease Status: For dynamically assigned IP addresses through DHCP, monitoring the lease status of IP addresses is crucial. DHCP servers maintain lease records for assigned IP addresses, indicating the duration of the lease and the associated devices. Administrators can verify lease durations and renewal processes to ensure that devices retain valid IP addresses and that the DHCP server effectively manages address allocation.

3. Switch Port Status: Network switches provide insights into the status of individual switch ports and the devices connected to them. Administrators can verify the association of assigned IP addresses with specific switch ports, confirming that devices are connected to the appropriate ports and are successfully communicating within the network.

4. IP Address Conflict Resolution: Address conflicts can arise when duplicate IP addresses are assigned within the network, leading to connectivity issues and communication disruptions. Verifying the absence of IP address conflicts through network monitoring tools and conflict resolution procedures is essential for maintaining network stability and ensuring uninterrupted device communication.

5. Device Configuration Review: Reviewing the configuration settings of individual devices, including their assigned IP addresses, subnet masks, default gateways, and DNS server settings, provides a comprehensive overview of the network connectivity status. This review ensures that devices are configured with accurate network parameters, facilitating seamless communication and resource accessibility.

6. IPv6 Address Verification: In networks utilizing IPv6 addressing, administrators must verify the successful assignment and configuration of IPv6 addresses to devices. This involves confirming the presence of globally routable IPv6 addresses on devices and ensuring their compatibility with IPv6-enabled network services and applications.

By diligently verifying IP assignments through network discovery tools, DHCP lease monitoring, switch port status checks, and device configuration reviews, administrators can uphold the integrity and functionality of the network, ensuring that devices are equipped with valid and accessible IP addresses to facilitate efficient communication and data exchange.

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How to configure a static IP on Windows 10 or 11

Do you need to switch from a dynamic to a static IP address configuration on Windows 11 or 10? Here's how.

• Windows 11 static IP
• Windows 10 static IP

On Windows, the router's Dynamic Host Configuration Protocol (DHCP) server is (usually) responsible for assigning a dynamic Transmission Control Protocol/Internet Protocol (TCP/IP) configuration to every device in the network, including to your computer running Windows 11 or Windows 10.

Although a dynamic IP address is the recommended configuration for most situations, you may need to change to a static IP address if you're thinking about setting up a printer or file sharing, or you have to configure port forwarding on the router to your computer.

The reason is that a dynamic network configuration can change at any time after the lease from the DHCP expires and if the address changes, network resources you may have configured will stop working. Setting a static IP address will always stay the same on the computer, allowing a more reliable experience sharing resources in the network or forwarding ports.

Whatever the reason, on Windows 10 and 11, you have many ways to configure a static TCP/IP address, including using the Settings app and Command Prompt.

This guide will walk you through the different ways to configure a static network configuration on Windows 11 and 10.

How to set a static TCP/IP network configuration on Windows 11

On Windows 11, you can change your computer's dynamic IP configuration to static in at least two ways through the Settings app or commands.

Configure IP from Settings app

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To assign a permanent TCP/IP configuration on Windows 11, use these steps:

• Open  Settings .
• Click on  Network & internet .
• (Optional) Click on Advanced network settings .
• Under the "More settings" section, click on Hardware and connection properties.
• Note the current IPv4 ,  Subnet mask ,  Default Gateway , and  DNS server addresses to determine the new configuration, as it has to be in the same network scope.
• Click the  Ethernet  or  Wi-Fi  page on the right side from the "Network & internet." page.

• Quick note:  If you select the Wi-Fi page, you need to click on the connection properties to access the network settings.
• Click on the  Edit  button for the "IP assignment" setting.

• Select the  Manual  option from the drop-down menu.
• Turn on the  IPv4  toggle switch.
• Confirm the IP address for the computer – for example, 10.1.4.90.
• Confirm the subnet mask for the configuration – for example, 255.255.255.0.
• Confirm the default gateway address (usually your router's IP) – for example, 10.1.4.1.
• Confirm the preferred DNS address – for example, 10.1.4.1.

•   Quick note:  In a home network, you may also be able to use the router's IP address for the DNS configuration. You can also use third-party DNS services like Google Public DNS, Cloudflare, Cisco's OpenDNS, and others. 
• (Optional) Select the  "On (automatic template)"  option for the "DNS over HTTPS" setting and leave the  "Fallback to plaintext"  option disabled unless you want to encrypted as well as unencrypted traffic or you're troubleshooting connectivity.
• Quick note:  DNS over HTTPS (DoH) is a feature that encrypts the DNS queries over the HTTPS protocol to improve security and privacy on the internet. You only want to enable this feature if the DNS server supports this feature.
• Confirm the alternate DNS address (if applicable).
• (Optional) Select the  "On (automatic template)"  option for the "DNS over HTTPS" setting and leave the  "Fallback to plaintext"  option disabled.
• Click the  Save  button.

Once you complete the steps, the computer will start using the static network configuration. If everything has been configured correctly, you should be able to open the web browser to access the internet.

If you entered an address (such as the DNS address) and then changed it, you probably won't be able to save the settings. If this is the case, cancel the configuration, start over, enter the correct configuration, and then try to save the settings.

Configure IP from Command Prompt

To set a static TCP/IP configuration on Windows 11, use these steps:

• Open  Start .
• Search for  Command Prompt , right-click the top result, and select the  Run as administrator  option.
• Type the following command to see your current networking configuration and press  Enter : ipconfig /all
• Confirm the name of the adapter and the networking configuration, including the IPv4 , Subnet mask , Default Gateway , and DNS Servers .

• Type the following command to configure a static TCP/IP address and press  Enter :  netsh interface ip set address name= "ADAPTER-NAME" static IP-ADDRESS SUBNET-ADDRESS DEFAULT-GATEWAY-ADDRESS

In the above command, replace  ADAPTER-NAME  with the name of your network adapter. Change  IP-ADDRESS SUBNET-ADDRESS    DEFAULT-GATEWAY-ADDRESS  with the device IP address, subnet mask, and default gateway addresses you want. For example, this command sets the 10.1.4.90, 255.255.255.0, 10.1.4.1 configuration:  netsh interface ip set address name="Ethernet 10Gb" static 10.1.4.90 255.255.255.0 10.1.4.1

• Type the following command to set a DNS server address and press  Enter :  netsh interface ip set dns name="ADAPTER-NAME" static DNS-ADDRESS  

In the command, change  ADAPTER-NAME  with your adapter's name and  DNS-ADDRESS  with the DNS server address of the network. For example, this command sets the local router as the DNS server:  netsh interface ip set dns name="Ethernet 10Gb" static 10.1.4.1

• Type the following command to set an alternate DNS server address and press  Enter :  netsh interface ip add dns name="ADAPTER-NAME" DNS-ADDRESS index=2

In the command, change  ADAPTER-NAME  with the adapter's name and  DNS-ADDRESS  with an alternate DNS server address. For example, netsh interface ip add dns name="Ethernet 10Gb" 1.1.1.1 index=2

After you complete the steps, the commands will set a static network configuration on Windows 11.

How to set a static TCP/IP network configuration on Windows 10

On Windows 10, you can also use the Settings app and Command Prompt to set up a static IP network configuration.

To assign a permanent TCP/IP configuration on Windows 10, use these steps:

• Click on  Ethernet  or  Wi-Fi .
• Click on the active connection on the right side.

• Click the  Edit  button for the "IP assignment" setting.

• Select the  Manual  option.
• Confirm the subnet prefix length (subnet mask) for the configuration – for example, 24 to specify the 255.255.255.0 subnet mask.

• Quick tip:  It's important to use the number that represents the network instead of the subnet mask. Otherwise, the configuration won't save. If you don't know the subnet prefix length for your subnet mask, you can use any  online subnet calculator  to find out.

Once you complete the steps, Windows 10 will start using the static IP configuration. If you lose network connectivity, restart the computer to regain access to the local network and internet.

To change from dynamic to static IP address with commands on Windows 10, use these steps:

In the command, change  ADAPTER-NAME  with your adapter's name and  DNS-ADDRESS  with the DNS server address of the network. For example, this command sets the local router as the DNS server:  netsh interface ip set dns name=" Ethernet 10Gb" static 10.1.4.1

In the command, change  ADAPTER-NAME  with the adapter's name and  DNS-ADDRESS  with an alternate DNS server address. For example, netsh interface ip add dns name="Ethernet0" 1.1.1.1 index=2

After you complete the steps, the network configuration will switch from dynamic to static on Windows 10.

Mauro Huculak is technical writer for WindowsCentral.com. His primary focus is to write comprehensive how-tos to help users get the most out of Windows 10 and its many related technologies. He has an IT background with professional certifications from Microsoft, Cisco, and CompTIA, and he's a recognized member of the Microsoft MVP community.

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IANA IPv4 Address Space Registry

Resolving virtual machine IP address conflict issues (1008177)

• The system has detected a conflict for IP address
• There is an IP address conflict with another system on the network
• The static IP address that was just configured is already in use on the network. Please reconfigure a different IP address

Resolving IP address conflicts

• For network environments with statically assigned IP addresses, ensure each local host is configured with a unique IP address. If your computer has a dynamically assigned address, releasing and renewing its IP address can workaround IP address conflicts.
• Clear the ARP table of the LAN switch

Assign a new IP address that has never been used if that option is available. First ping test the IP address before assigning it to confirm its availability.

Resolving TCP/IP stack issues on the virtual machine

To resolve TCP/IP stack issues on the virtual machine:

• Remove and reinstall your virtual network adapter driver.

Verify, using the vSphere/ VI Client, that the ethernet adapter is connected and powered:

Enable and disable the NIC and ping test.

Uninstall VMware Tools and ping test.

Connect to host using the vSphere/ VI Client.

Turn off the virtual machine.

Remove the ethernet adapter.

Turn on the virtual machine. TCP/IP is not loaded.

Turn off the virtual machine again.

Add the ethernet adapter – at this point either auto assign a MAC or manually assign one.

Assign a different IP address to eliminate the possibility of duplicate IP and do a ping test.

Reinstall VMware Tools and do a ping test.

For related information, see Verifying virtual network adapter is present and connected to the virtual machine (1003786) .

If there is a problems with assigning the IP address to the Virtual network adapter please see the following article Networking Error, IP Address Already Assigned to Another Adapter (1179) .

Como solucionar problemas de conflito de endereço IP em máquinas virtuais Resolución de problemas de conflictos de direcciones IP de máquinas virtuales 解决虚拟机 IP 地址冲突问题 仮想マシンの IP アドレスの競合問題を解決する

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